1. Field of the Invention
The present Invention relates to a high-frequency semiconductor hybrid integrated circuit device comprising a high-frequency circuit Including a transistor for amplifying a high-frequency electric power, and a peripheral circuit, such as a matching circuit, for the high-frequency circuit.
2. Description of the Related Art
FIG. 6 is a perspective view showing a discrete transistor mounting portion of a conventional high-frequency semiconductor hybrid integrated circuit device. In FIG. 6, a dielectric substrate 2 is adhered to the heat radiating plate 1 by soldering. The dielectric substrate 2 has a peripheral circuit 50 shown in phantom lines including a matching circuit for a high-frequency circuit. The dielectric substrate 2 further includes a hole 2a for mounting a heat sink 3 on which a discrete transistor is mounted. The heat sink 3 is formed of an insulating material having a desirable heat conductivity (low heat resistance). A MOS-type capacitor 4 and a transistor chip 5 are mounted on the heat sink 3.
An input conductive film 6a and an output conductive film 7a are printed on the dielectric substrate 2, while an input conductive film 6b and an output conductive film 7b are printed on the heat sink 3. The output conductive film 7a also acts as a bias line for the transistor chip 5. Further, grounding conductive films 8a and 8c are printed on the surface of the heat sink 3. The input lead 12 is coupled to the input conductive films 6a and 6b while the output lead 13 is coupled to the output conductive films 7a and 7b, and both of leads 12 and 13 are fixed to the conductive films by soldering. The input lead 12, the MOS-type capacitor 4 on the ground conductive film 8c, a ground conductive bridge 14, and the transistor chip 5 on the output conductive film 7b are coupled through bonding wires 11 composed of e.g. Au.
For a simple description of the operation of the device, the high-frequency power is applied to the transistor chip 5 through the input conductive film 6a, the input lead 12, the input conductive film 6b, the bonding wire 11, and the MOS-type capacitor 4. The input high-frequency power is amplified in the transistor chip 5. The amplified high-frequency power is then output through the output conductive film 7b, output lead 13, and the output conductive film 7a. The heat generated by the amplifying operation flows out of the integrated circuit device through the heat sink 3 and the heat radiating plate 1.
A conventional high-frequency semiconductor hybrid integrated circuit has been composed as mentioned above. In a high-frequency circuit, it is desirable for obtaining excellent high-frequency characteristics, in particular, to form a so-called uniformly distributed constant line path in which the constants of resistance, inductance, and capacitance are uniformly distributed along a line path. However, in the conventional device, a significant floating capacitance is produced at the input lead 12 and the output lead 13, which greatly differs from the capacitance at the input/output conductive films 6a, 6b, 7a and 7b, thereby causing the circuit constant along the line path to be non-uniform. This worsens the high-frequency characteristics of the high-frequency circuit. FIG. 7 is an equivalent circuit showing a distribution of the circuit constants of a input line path around the input conductive films 6a and 6b and the input lead 12 in FIG. 6. This equivalent circuit is composed of a plurality of inductances La (the resistance component is omitted), and capacitances Ca and C12 between these conductive films 6a, 6b and the heat radiating plate at the ground level. Thus, in the conventional device, the stray capacitance at the input lead 12, i.e., the capacitance C12, was larger than that at the input conductive films 6a and 6b i.e., the capacitance Ca. The same is true at the output lead 13 side.
Further, in the manufacturing process of such a conventional device, a fitting process for the input/output leads 12, 13 and the ground bridge 14 etc. is required, therefore it is difficult to save labor.
Furthermore, since the heat sink 3 for mounting the discrete transistor is square, it is necessary to form the hole 2a of the dielectric substrate 2 a in square shape which causes stress to concentrate at the corners of the hole 2a, thereby cracking the substrate 2.